Intensive hand training can improve dexterity in children with hemiplegic cerebral palsy. Two categories of training paradigms have been tested. In constraint-induced movement therapy (CIMT), the less-affected upper extremity (UE) is restrained while the affected UE is trained. Intensive bimanual training (e.g., Hand-arm bimanual intensive training (HABIT)) encourages children to use both UEs in bimanual tasks. However, it has been reported that children whose impaired UE is controlled via ipsilateral corticospinal (CS) connections show less recovery in CIMT than children whose impaired UE is controlled by contralateral CS connections. This raises the interesting possibility that there is a interaction between treatment type and CS connection pattern. Limited use of an UE drives down activity in the contralateral motor cortex (M1). In children with contralateral control of the affected UE, decreasing activity in the healthy M1 gives the affected side a competitive advantage over the other side. In contrast, in children with ipsilateral control of the affected UE the healthy M1 controls the affected UE. Constraining the less-affected UE drives down activity in the healthy M1, which may impede recovery of the impaired UE. The PIs will further investigate this important issue. They will use single-pulse transcranial magnetic stimulation to probe M1 function in children who have previously received HABIT or CIMT. The PIs hypothesize that children with ipsilateral connectivity of the affected hand showed greater improvement in dexterity after HABIT, compared to CIMT. Importantly, they will help determine whether children with ipsilateral CS projections would best benefit from bimanual therapy vs. CIMT.